1. The Field of the Invention
The present invention relates to the field of information sensors for rolling-contact bearings. It relates more particularly to an encoder element intended to interact with a sensor of active type such as Hall-effect or magnetoresistive probes, for the purpose of detecting the speed of rotation of the bearing.
2. The Prior Art
Information sensors for bearings are currently used as devices for detecting the speed of rotation of the bearing for a motor vehicle equipped with a wheel anti-lock braking system or ABS. The information sensor assemblies comprise an encoder element rendered integral with a rotating race of the bearing and a sensor mounted so that it is stationary with respect to a non-rotating race of the bearing. The encoder element and the sensor are located facing one another axially or radially with a slight air gap. The encoder element driven in terms of rotation by the rotating race creates variations in magnetic field. The sensor detects these variations in magnetic field, converting them into an electrical signal the frequency of which is representative of the speed of rotation of the bearing. The signal coming from the sensor is transmitted via an electrical cable to a control and processing unit of the vehicle.
French Patent Application No. 2,599,794 makes known an information sensor assembly for a bearing in which the encoder element is produced in the form of a multipolar ring integral with the rotating race of the bearing and filing past, in terms of rotation, in front of an active sensor of the Hall-effect probe type. However, the manufacture of a multipolar ring, especially when the ring includes a great number of alternate magnetic poles, is relatively tricky from the point of view of the accuracy of the magnetization. The accuracy of the magnetization of the multipolar ring is essential to ensure a good detection signal which requires the smallest possible spread in the dimensional and magnetic characteristics of the poles of the multipolar ring.